Yazar "Erulas, Fatih Ahmet" seçeneğine göre listele

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    Accurate and sensitive determination of lead in black tea samples using cobalt magnetic particles based dispersive solid-phase microextraction prior to slotted quartz tube-flame atomic absorption spectrometry
    (Elsevier Sci Ltd, 2019) Akkaya, Erhan; Erulas, Fatih Ahmet; Buyukpinar, Cagdas; Bakirdere, Sezgin
    Newly developed combination of magnetic cobalt particles based dispersive solid-phase microextraction (Co-MP-DSPME) and slotted quartz tube attached flame atomic absorption spectrometry (SQT-FAAS) was utilized to determine lead at trace levels in tea samples. Co-MPs' adsorbent properties were tested and validated for their selectiveness to lead. Only with a few and short extraction steps (i.e. adding MPs, mixing, decanting and eluting) analyte was extracted from sample solution rapidly and efficiently. Limit of detection (LOD) and limit of quantification (LOQ) for the developed method (Co-MP-DSPME-SQT-FAAS) were found to be 7.77 mu g/L and 25.9 mu g/L, respectively. Matrix matching strategy was performed and outcomes indicated that the developed method is applicable with the high percent recovery values of 110.1 +/- 4.5 and % 102.9 +/- 4.2 for 100 and 300 mu g/kg lead standard spiked black tea samples, respectively. The method was also applied to standard reference material to check the accuracy of the method.
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    Determination of levetiracetam by GC-MS and effects of storage conditions and gastric digestive systems on drug samples
    (Newlands Press Ltd, 2021) Erulas, Fatih Ahmet; Chormey, Dotse Selali; Oz, Ersoy; Bakirdere, Sezgin
    Background: Epilepsy is a neurologic condition that is occurs globally and is associated with various degrees of seizures. Levetiracetam is an approved drug that is commonly used to treat seizures in juvenile epileptic patients. Accurate quantification of the drug's active compound and determining its stability in the stomach after oral administration are important tasks that must be performed. Results & methodology: Levetiracetam was extracted from drug samples and quantified by gas chromatography mass spectrometry using calibration standards. Stability of levetiracetam was studied under various storage conditions and in simulated gastric conditions. The calibration plot determined for levetiracetam showed good linearity with a coefficient of determination value of 0.9991. The limits of detection and quantification were found to be 0.004 and 0.014 mu g center dot ml(-1), respectively. The structural integrity of levetiracetam did not change within a 4-h period under the simulated gastric conditions, and no significant degradation was observed for the different storage temperatures tested. Discussion & conclusion: An accurate and sensitive quantitative method was developed for the determination of levetiracetam in drug samples. The stability of the drug active compound was monitored under various storage and gastric conditions. The levetiracetam content determined in the drug samples were within +/- 10% of the value stated on the drug labels.
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    Oleic and stearic acid-coated magnetite nanoparticles for sonication-assisted binary micro-solid phase extraction of endocrine disrupting compounds, and their quantification by GC-MS
    (Springer Wien, 2019) Chormey, Dotse Selali; Akkaya, Erhan; Erulas, Fatih Ahmet; Bakirdere, Sezgin
    Nanosized magnetic nanoparticles (MNPs) were utilized for the preconcentration of 12 analytes including pesticides, alkylphenols, hormones and bisphenol A prior to their determination by GC-MS. The extraction efficiency of the MNPs was enhanced by coating them with oleic acid and stearic acid. A binary system consisting of the two kinds of coated MNPs was optimized using a multivariate experimental design which evaluated main experimental variables and their interactions. Under optimized conditions, the following figures of merit are found: (a) Enrichment factors ranging from 64 to 345; (b) detection limits between 0.13 and 2.7 mu g L-1; and (c) recoveries from spiked underground well water and municipal wastewater between 90 and 109%. The closeness of the results to 100% validated the method and underpinned its trueness for quantitative determinations.
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    Sensitive determination of nickel at trace levels in surface water samples by slotted quartz tube flame atomic absorption spectrometry after switchable solvent liquid-phase microextraction
    (Springer, 2020) Erulas, Fatih Ahmet
    In this study, switchable solvent (SS) for liquid-phase microextraction (LPME) was used as a tool to preconcentrate nickel from aqueous samples for determination by flame atomic absorption spectrometry. The SS-LPME method was optimized thoroughly to boost the absorbance signal of nickel for trace level determination. Parameters optimized included switchable solvent volume, sodium hydroxide concentration, sodium hydroxide volume, and eluent volume. The SS-LPME method enhanced the detection power by about 32-folds, and a slotted quartz tube (SQT) was used to obtain 2.6-folds increase in detection power. The combination of LPME and SQT-FAAS produced 104-folds enhancement, correlating to a limit of detection value of 1.8 mu g/L. Low relative standard deviations calculated for the lowest calibration concentration indicated good repeatability for replicate measurements. Accuracy of the optimized method and its applicability to real samples was tested on two river samples. The results (85-103%) obtained from the spike recovery experiments were satisfactory.
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    Simultaneous Determination of Chromium Species in Water and Plant Samples at Trace Levels by Ion Chromatography-Inductively Coupled Plasma-Mass Spectrometry
    (Taylor & Francis Inc, 2019) Sel, Sabriye; Erulas, Fatih Ahmet; Turak, Fatma; Bakirdere, Sezgin
    Ion chromatography-inductively coupled plasma-mass spectrometry (IC-ICP-MS) was used for the identification and quantification of chromium species. Chromium(III) and chromium(VI) were separated and determined by IC-ICP-MS. The separation was achieved using an anion exchange column with 0.55 M HNO3 as mobile phase. It was a particular goal of this work to exclusively use nitric acid for elution in order to reduce interferences in the ICP-MS system. Analytical figures of merit were calculated under the optimum conditions by developing calibration plots in a concentration range of 0.50-250 mu g/L for both species. The detection limits for Cr(III) and Cr(VI) were 0.09 and 0.03 mu g/L, respectively. Spiked recovery tests were used to evaluate the applicability of the analytical method in environmental samples, and the recoveries ranged between 97 and 103% for both analytes. The accuracy of the method for total chromium content was validated through the analysis of a spring water-certified reference material (UME 1201), and the obtained results were in good agreement with the certified value. Lettuce seedlings were cultivated to evaluate the intake levels of these species. In addition, the bioaccessibility of Cr(III) and Cr(VI) from the lettuce seedlings in simulated gastric and intestinal fluids media was examined.
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    Simultaneous Determination of Harmful Aromatic Amine Products of Azo Dyes by Gas Chromatography-Mass Spectrometry
    (Pleiades Publishing Inc, 2020) Chormey, Dotse Selali; Zaman, Buse Tugba; Maltepe, Esra; Buyukpinar, Cagdas; Bulgurcuoglu, Ayse Evrim; Turak, Fatma; Erulas, Fatih Ahmet
    Azo dyes constitute about 66% of all colorants and they are widely used in industries such as textiles, plastics, ceramics, cosmetics and food. However, due to the reductive cleavage of some azo dyes into carcinogenic aromatic amines, many countries have set concentration limits or have banned the use of these azo dyes. Selected aromatic amines that pose health risk to consumers were simultaneously determined by gas chromatography mass spectrometry. A good linearity in calibration plot was obtained for the analytes and the low relative standard deviations indicated high instrumental precision. A recovery test was performed to validate the extraction method and the results obtained were between 92-114%. The method was applied to the analysis of real samples and the concentrations of aromatic amines detected were below the 30 mg/kg limit set by regulatory authorities.